Technical Abstract:
Gibberella pulicaris (Fries) Sacc. (anamorph: Fusarium sambucinum Fuckel), is the primary causal agent of Fusarium dry rot of stored potatoes worldwide. This disease causes extensive losses in tuber quality and marketable tubers. Dry rot is not effectively controlled by fungicides and all commonly grown potato varieties are susceptible. Biological control of fFusarium dry rot is an attractive control alternative due to the etiology of the pathogen and the favorable conditions for microbial activity that exist in potato storages. Eighteen bacterial strains highly effective in controlling Fusarium dry rot were isolated from suppressive microbial communities capable of rapidly colonizing microbially depleted substrates including potato periderm. In a process deemed "two dimensional liquid culture focusing," microbes were ranked using a combination of the efficacy of a strain and the growth kinetics of that strain in liquid culture. The advantages of rating putative biocontrol agents for both efficacy and potential for commercial development are discussed. Antibiosis is a mechanism of biocontrol for some strains active against dry rot, though strains may also induce host resistance or produce volatile inhibitors of fungal activity. Combining two biocontrol strains can greatly decrease the total number of cells necessary to control Fusarium dry rot. Reducing the number of cells required for an effective dose would at least partially offset cost disadvantages potentially associated with industrially producing more that one microbial strain. Future research directions in developing a biocontrol product active against Fusarium dry rot of potatoes include tailoring liquid culture protocols to produce cells optimized to survive drying, storage and rehydration.